1. Field of the Disclosure
This disclosure relates generally to power management with flip-flops that are deployed in an integrated circuit (IC) and, more specifically, to controlling multiple flip-flops with each flip-flop having a retention feature including a live slave portion and a collapsible master portion.
2. Description of Related Art
Power consumption of electronic devices is an increasingly important factor in electronic device design. From a global perspective, energy demands of electronic devices occupy a sizable percentage of total energy usage due to large corporate data centers and the ubiquity of personal computing devices. Environmental concerns thus motivate efforts to lower the power consumption of electronic devices to help conserve the earth's resources. From an individual perspective, in addition to a universal desire to have lower energy bills, many personal computing devices are powered by batteries. The less energy that is consumed by a portable battery-powered electronic device, the longer the portable device may operate without recharging the battery. Lower energy consumption also enables the use of smaller batteries and the adoption of thinner form factors to make devices that are more portable. Therefore, the popularity of portable electronic devices also motivates efforts to lower the power consumption of electronic devices.
An electronic device consumes power if the device is coupled to a power source and is turned on. Although this power consumption scenario is true for the entire electronic device, the consumption scenario is also true for individual parts of the electronic device. Hence, power may be conserved if parts of an electronic device are decoupled from power or turned off even while other parts remain powered and turned on. Entire discrete components of an electronic device, such as a whole integrated circuit (IC) or a display screen, may be decoupled from power or turned off. Selected parts of a discrete component may likewise be powered down. For example, an integrated circuit processing entity, such as a core of an integrated circuit, may be powered down. Parts of an integrated circuit may be powered down intermittently if usage is regular but discontinuous, or may be powered down temporarily if usage has ceased for some arbitrary period of time.
Powering down part of an integrated circuit, such as a core, can save power and extend battery life. Unfortunately, powering down a core of an integrated circuit can also create problems. For example, resuming operations with a powered down core takes time, which can slow performance and adversely impact a user experience. Furthermore, operational data may be lost if power is removed from certain types of computer memory. Losing operational data may force an application to restart or permanently damage user files, such as documents or pictures. To avoid a loss of operational data, the operational data may be moved to a slower or remote memory location prior to a core of an integrated circuit being powered down. When a time to awaken the core to continue a computing task arrives, the operational data is retrieved from the memory location for further processing, but this retrieval operation delays the resumption of computing functionality from the powered down state.